The invention relates to an optimal active time-reversal focusing method based on iterative least square/pre-filtering. The method comprises the following steps: 1) sending source signals by a guide sound source, and conducting the operations of receiving, time-reversal and re-sending by a time-reversal array according to the conventional active time-reversal process, so as to acquire focusing signals at the location point of the sound source, wherein the source signals are wideband pulse signals with the bandwidth being 20Hz to 200kHz and the frequency range being within an audible sound or ultrasound frequency band range; 2) estimating a plurality of cascaded pre-filter time-domain responses used for carrying out the filtration treatment on the source signals on the basis of the iterative least square rule by combining the source signals and the focusing signals; and 3) re-sending the pre-filtered source signals by the guide sound source, and carrying out the operations of receiving, time-reversal and re-sending by the time-reversal array according to the conventional time-reversal process, so as to acquire the optimal focusing signal waveform at the location of the sound source. The invention can achieve the inverse-filtering and focusing effects within the time domains and recover the waveform of the source signals within the focusing region; the invention allows the random distribution of array elements and the difference in the frequency response among the array elements; and the invention has high spatial resolution.